Windows File Protection in Windows 2000

Windows File Protection is a security feature in Windows 2000 that prevents certain critical system files from being overwritten by other application that you may install on your system, thereby maintaining the integrity of your installation. The original copies of these system files are stored in a hidden folder called dllcache - by default all sys, dll, exe and ocx files from the original installation are stored here.Windows File Protection works in the background replacing rogue files without user intervention but a record of the event will be made in the System Event Log. This programme can be disabled, though this is not recommended, by opening the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SFCDisable

Setting this value to 1 will disable the feature, but you will be prompted to enable it each time you log on as an Administrator. Setting the value to 2 disables it without prompt. To enable the feature set the value to 0.

If you have limited hard disk space you may wish to reduce the size of the DLLCACHE directory. This can be done by editing the System File Checker Utility.

SYSTEM FILE CHECKER: This is a programme run from a Command Prompt, SFC.EXE, which allows an administrator to scan the system for system files that have been altered from the original installation. This programme can be run with several switches:

/SCANNOW Scans all protected system files immediately.
/SCANONCE Scans all protected system files once.
/SCANBOOT Scans all protected system files at every boot.
/CANCEL Cancels all pending scans of protected system files.
/QUIET Replaces all incorrect file versions without prompting the user.
/PURGECACHE Purges the file cache and scans all protected system files immediately.
/CACHESIZE=x Sets the file cache size (in megabytes).

If you wish to set the size of the DLLCACHE folder to zero, you would run "SFC /CACHESIZE=0" from a Command Prompt, then reboot and run "SFC /PURGECACHE" to delete the files. If you have Windows File Protection enabled and you have reduced the size of the DLLCACHE folder, you may be prompted to supply your Windows 2000 CDRom to complete the reinstallation of the original files.